Several technical trends have developed in the past two decades to achieve increased fuel economy of automotive vehicles. One such trend is to decrease the weight of the vehicle. When a vehicle is traveling at highway speeds, up to one-half of the force needed to propel the vehicle forward is due to the aerodynamic drag of the vehicle rather than the vehicle weight. Therefore, if the aerodynamic drag of a vehicle can be lessened, a significant increase in fuel economy can be achieved.
To achieve the above-noted technical trends of weight reduction and the lowering of aerodynamic drag a new type of bumper has been developed. The new type of bumper, often referred to as a fascia, is fabricated from a polymeric material which is lighter than most metals. Prior bumpers were steel and extended outward from the remainder of the car body. Fascias are typically formed in rounded shapes that blend into the contour of the remainder of the vehicle body. The shape of the fascia lowers aerodynamic drag of the vehicle. Additionally, the fascia can materially add to the styling enhancement of the vehicle. Yet another advantage of the fascia is that its color can be selected to match the color of the remainder of the car body.
A so-called clear coat technique (sometimes referred to as two-coat one-bake technique) is used to cover metal body panels of most cars and light trucks. The clear coat technique comprises applying a metallic base paint composition, called a top coat, containing an optional metallic pigment, to a steel substrate. The steel substrate is provided in advance with undercoat and intermediate coat primers. Then, without curing the resulting top coat paint film, a clear paint composition is applied over the top coat in a wet-on-wet manner. The top coat and clear paint are then cured simultaneously.
Prior to the present invention, most fascias were injection molded. The molded fascias were then painted with a color coat to match the paint on the metal vehicle body. A second clear coat of paint was then applied to the fascia so that the appearance of the fascia would match that of the remainder of the vehicle body. The color utilized to paint the fascia sometimes had to be modified because the resultant color of cured paint on the injection molded fascia sometimes would differ from the color of the paint on a steel substrate. Therefore, trial and error was required to get the colors on the fascia to match the color of the remainder of the car body.
A prior method to cover the fascia substrate included using a painted polymeric sheet of material. A clear coat of material was laminated to the painted sheet by a spray, dip coating or adhesive technique. Additional layers of material may have been added for processing or to add strength. The polymeric sheet was back formed and the polymeric substrate was then injection molded into the back side of the back form.
In another prior method the color imparted to the sheet material by a pigment application rather than a painted application. The top clear coat was added as in the previously described method. Both methods often resulted in delamination during the back forming process when the sheet material was bent as it was formed to cover the curved fascia.
These deficiencies in the art of providing matched colors between a fascia and the remainder of the vehicle body are similarly present in other automotive and non-automotive applications. Accordingly, it is desirable to provide a coating for use with an article wherein the color of the coating may be readily matched to the remainder of the article. Additionally, it is desirable to provide a covering sheet for an automotive vehicle body panel, especially a bumper fascia, which has a top coat/clear coat appearance and which can be formed into complex shapes without suffering delamination. Specifically, it is desirable to provide a coating for a fascia or similar body panel which is readily color matched to another colored automotive vehicle body panel.